Maybe Ridax would be the man to ask.

Martin

I thought BM2000 / BC2000 used the "new" Datalink? Anyway, I haven't seen a single word of description of the old Datalink format (the new/current format is semipublic as far as the frame structure goes). Unfortunately I don't own any of the old format devices, otherwise I would've scoped it a long time ago 🙂

Physically I suppose it is a wired-or bus just lke the current, so the arbitration is similar to I2C: a device sending on the bus must monitor it and detect a collision if the bus wire doesn't agree at any time while sending a high level. At a previous job I had the immense displeasure to maintain some old 8048 code - as far as I remember, at least some of the ports are pseudo-bidirectional just as in 8051. Write a 1 to the port and it activates a weak internal pullup that can be easily driven low by an external signal. Many of the earlier B&O Datalink devices that use either of these processor families have the Datalink buses wired more or less directly to a port pin. Definitely none of them use the UART, the message frames are too long for that.

I guess the pin 6/7 distinction was there to encourage people to connect the devices to the correct input 🙂 When the RIAA preamp was moved from the receivers to the turntables, the Datalink pin changed as well.

As an interesting piece of trivia, all B&O Datalink implementations until 1997 or so contain a bug in the collision detection that occasionally causes messages to be lost. Apparently the protocol contained a few thousand lines of decade old assembly code which was also the main documentation. The bug had proved impossible to trace conventionally, but was finally nailed using a formal state-transition graph analyzer. There was an Aalborg(?) University CS report on this, I'll post the link if I ever manage to find it again.

EDIT: Found the report - it was published in link (you need IEEE Xplore access from an academic library, or otherwise, to download the full text), and the unpublished version can be found

tournedos wrote:

the new/current format is semipublic as far as the frame structure goes

Have you got any documentation/lins about the protocol... I'll be really interested.

Google for "datalink.zip". There used to be a broken link for it in Beotech - might actually be on site somewhere nowadays. The IR remotes use the exactly same data format (but obviously L level on bus  = 455 kHz carrier on).

EDIT: Yes it's on site - rather confusingly as the MCL2 technical service manual.

tournedos wrote:

Google for "datalink.zip". There used to be a broken link for it in Beotech - might actually be on site somewhere nowadays. The IR remotes use the exactly same data format (but obviously L level on bus  = 455 kHz carrier on).

EDIT: Yes it's on site - rather confusingly as the MCL2 technical service manual.

I had a look around the manual and found out that it describes the data link format for Beosystem 5000, Beolink 1000, Beovision MX5xxx and other models of the series. That includes the (later models) Beomasters 3500 and 4500, but not the 2000, which uses the old data link format.

The document does mention that the 'old format' is compatible with the new format, meaning the basic signal timing is identical but only new address and command codes may be added. However, I also recall a mention of some Datalink devices being incompatible with each other (e.g. a 2000 series Beomaster with a 4002 Beogram and the like).

Is there a difference between those formats as well? I'd really like to upgrade my Beosystem with a tangential tracking turntable, but I want one that can be controlled from my Beomaster. Not being sure of that kept me off purchasing one for the time being.

EDIT: I got a hold of the IEEE document (hey, it helps when you're an EE student, free IEEE Xplore access!) and there's enough data on there to make a complete implementation of the Beolink (new style) protocol in something like an AVR. I'm not really sure how much of which we could publish it, however, because I'm quite clueless as to when the relevant patent(s) would expire.

Goddammit I hate it when you write a lengthy reply and the forum eats it! 😜 I'll try once more with as much as I still remember...

Stoney3K wrote:

The document does mention that the 'old format' is compatible with the new format, meaning the basic signal timing is identical but only new address and command codes may be added. However, I also recall a mention of some Datalink devices being incompatible with each other (e.g. a 2000 series Beomaster with a 4002 Beogram and the like).

Is there a difference between those formats as well? I'd really like to upgrade my Beosystem with a tangential tracking turntable, but I want one that can be controlled from my Beomaster. Not being sure of that kept me off purchasing one for the time being.

EDIT: I got a hold of the IEEE document (hey, it helps when you're an EE student, free IEEE Xplore access!) and there's enough data on there to make a complete implementation of the Beolink (new style) protocol in something like an AVR. I'm not really sure how much of which we could publish it, however, because I'm quite clueless as to when the relevant patent(s) would expire.

A DIY project, which would probably be only point-to-point communication, will manage with a much simpler implementation that doesn't  care about collision detection. That would mostly be an issue on an MCL bus with multiple devices, like a multiroom installation.

The "future, more automated version of the protocol" mentioned in that document must be Masterlink.

Where can I find these documents? I have been looking for these for a while. They would be very useful for a project I am doing.

Thanks in advance for your help.

Phil, as I said the MCL2 technical manual is on site, and the other one really contains nothing you wouldn't already know after reading the MCL2 doc (and I already posted a direct link to the freely available version of the latter). It's not really a technical document on Datalink, just a case study on an unrelated software tool.

Stoney3K wrote:

Is there a difference between those formats as well? I'd really like to upgrade my Beosystem with a tangential tracking turntable, but I want one that can be controlled from my Beomaster. Not being sure of that kept me off purchasing one for the time being.